Three new American reality TV shows have been unveiled - including one involving Oscar-winning actors Matt Damon and Ben Affleck.

Damon and Affleck are working as executive producers on The Runner, which will be screened by ABC and will follow one person running across America as viewers try to catch him.

ABC, along with other networks Fox and CBS, will hope that there is still a large enough public appetite for the format that has become a worldwide broadcasting phenomenon over the last two years.

Damon and Affleck: Executive producers

The networks also announced that they will continue to make their existing reality TV shows - Survivor on CBS, The Mole on ABC and Temptation Island on Fox.

The Runner will feature one person on a cross-country trip, aided by a former CIA agent.

Viewers will be given clues as to their whereabouts, and will win a cash prize if they track him down.

CBS's new show, The Great Race, will have a $1m (£700,000) prize for contestants - who will trek around the world in pairs.

Viewers will be able to follow their progress and the teams who fall behind in the race will be eliminated.

Strike threat

The third new reality TV show to be unveiled, Fox's End Game, includes actors who will live among real residents of an American town.

Contestants will have to track down a villain who is on the loose.

Networks will also use the shows to help fill their schedules if threatened strikes by screen actors and writers go ahead.

Reality TV shows are a mixture of documentaries, dramas and game shows, and put normal people into unscripted, unpredictable situations. They often have an element of audience participation and rivalry between contestants.

Big Brother was one such show which became a huge success in Britain last year, with the format recently resurrected for a celebrity version in aid of the Comic Relief charity.